1. Field of the Invention
The present invention relates to an ultraviolet and/or visible light curing photopolymerizable composition and a dry film resist and, more specifically, it relates to an ultraviolet and/or visible light curing photopolymerizable composition which can serve as a material for etching or plating resists, solder mask resists, and dry film resists as photosensitive organic films used in the formation of partitions for plasma display panels, and in the production of color filters employed in liquid crystal displays, as well as in the fields of printed circuit board production, metal working and printing plate making; it more particularly relates to an ultraviolet and/or visible light curing photopolymerizable composition which is highly sensitive to ultraviolet light, visible light or light in the wavelength range from ultraviolet light to visible light, and has excellent properties as a resist, as well as to a dry film resist employing it. Here, "ultraviolet light" refers to light of wavelength from 200-400 nm, and visible light is light of wavelength from 400-780 nm.
Ultraviolet and/or visible light sensitivity according to the present invention means both photosensitivity to either ultraviolet or visible light and photosensitivity to both ultraviolet and visible light, while an "ultraviolet and/or visible light curing photopolymerizable composition" means a composition which can be cured by light irradiation in the wavelength range of either ultraviolet or visible light, or both.
2. Description of the Related Art
Recent photoresists widely used for the preparation of printed circuit boards are the so-called "dry film photoresists" which are produced by sandwiching a photopolymerizable resin between a support film and a protective film. The photopolymerizable resin is usually an alkali developing type, with the unexposed portions are removed with an aqueous alkali solution upon development.
The method for using alkali developing dry film resists involves first releasing the protective film from the dry film while thermally laminating the photopolymerizable resin side onto a copper-clad laminate sheet, and then adhering a phototool to the support film side of the resist film and curing the sections to be cured by exposure to ultraviolet light rays or the like. Then, after releasing the support film, the unexposed portions are removed by development with a weak aqueous alkali solution of sodium carbonate or the like, to obtain a circuit pattern in the resist.
When using the copper throughhole method, the copper is subsequently etched, and the cured resist is released with a strong aqueous alkali solution of sodium hydroxide or the like to obtain a printed circuit board. When using the solder throughhole method, after copper plating or solder plating is accomplished the cured resist is released with a strong aqueous alkali solution, and the exposed copper is etched to obtain a printed circuit board.
In the steps described above, the dry film resist must of course have adequate properties as an etching resist, and therefore much research has been carried out in order to improve its resistance.
On the other hand, with recent advances in laser and light-emitting diode scanning exposure technology, a technique known as "direct imaging" has been developed whereby direct scanning exposure is accomplished with a laser or light-emitting diode instead of the conventionally used phototools, and this technique has been applied to plate making and the like.
For this direct imaging technique, methods have been developed for obtaining resist circuit patterns by scanning exposure of dry film resists using a lasers or light-emitting diodes without phototools, but since conventional dry film resists are photosensitive only to ultraviolet light, and their photosensitivity is low, they cannot be used for direct imaging.
It has therefore been desired to develop dry films made of ultraviolet and/or visible light curing photopolymerizable compositions with high sensitivity and scanning exposure ability not only with respect to ultraviolet light but also to visible light, and even to the transmitting wavelength of lasers, especially visible light lasers such as argon lasers with a wavelength of 488 nm and YAG lasers with a wavelength of 532 nm, as well as GaN light-emitting diodes of wavelength 478 nm.
Japanese Unexamined Patent Publication No. 3-126708, for example, describes ultraviolet sensitivity of a crosslinked curable composition comprising a specific thermoplastic polymer and a crosslinking monomer with at least 2 ethylenic unsaturated groups per molecule, but the photosensitivity to lasers and light-emitting diodes is not investigated, nor is any indication given of the visible light photosensitivity. Also, Japanese Unexamined Patent Publication No. 7-261407 describes a method of curing a visible light-curing resist and mentions a number of photopolymerization initiators used in compositions, but the systems do not include organic boron compounds. In addition, Japanese Unexamined Patent Publication No. 1-35548 and No. 1-298348 disclose photopolymerizable compositions containing photopolymerizable compounds with ethylenic unsaturated groups and linear organic polymers which also contain organic cationic dyes and organic boron compounds, but, in order to exhibit their effect, it has been necessary to further include a photopolymerization initiating triazine compound or morpholine compound.